In the burning of petroleum fuels in an internal combustion engine, hydrocarbons in the fuel and nitrogen and oxygen from the air used to combust the fuel combine to yield various oxides and nitrides, principally comprising carbon monoxide, carbon dioxide, nitrous oxide and nitric oxide. Waste materials in the fuel, such as sulphur produce other oxides such as sulphur dioxide. Additionally, some of the fuel passes into the exhaust partially combusted or uncombusted.
Often the particular oxides are more harmful to human beings than other oxides of the same elements. For example carbon dioxide may pose less of a hazard than carbon monoxide. In order to minimize the more harmful emissions, most larger internal combustion engines, particularly those used in automobiles are equipped with exhaust gas catalysts in their exhaust systems (“catalytic converters”) to convert less desirable oxides to more desirable oxides.
Automobiles generally have a fair amount of space available for both a catalytic converter and for noise abatement apparatus such as a muffler and a resonator to suppress the noise ordinarily associated with internal combustion engine operation.
Smaller engines in applications such as lawnmowers are significant generators of pollutants but in the past have seldom if ever been equipped with exhaust treatment apparatus, despite that for their size they often generate proportionately more harmful emissions. A reason for this may be the lack of expensive and sophisticated engine management systems found in more expensive applications such as automobiles.
It is an object of the present invention to provide a catalytic muffler of compact dimensions which is easily accommodated in small displacement internal combustion engine applications.
It is a further object of the present invention to provide such a compact catalytic muffler which also has noise attenuation capabilities to obviate the need for a separate muffler.
It is also an object of the present invention to provide a noise abating catalytic muffler design for small engine applications which is simple and comparatively inexpensive to produce and which lends itself readily both to O.E.M. and retrofit applications.